A ring-spinning machine customarily comprises a drafting frame in which, at each of a multiplicity of stations, usually along each side of the machine, the drafting frame having a pair of output rollers from which the yarn is delivered to a respective spindle at each station, usually through a thread guide or yarn guide which can be an eye upstream of the spindle.
The spindles, which can receive core sleeves on which the yarn is wound, cooperate with a traveler rings which sweeps around a guide or track ring on the ring rail so as to deposit the yarn in a bobbin. The balloon of yarn formed around the bobbin can be somewhat confined by a constriction ring which like the ring rail and/or the spindle rail can be vertically displaceable.
In such systems, the twist which is imparted to the yarn is predominantly produced in the region between the last pair of rollers of the drafting frame, and the point at which the yarn encounters the spindle. It is a common practice to provide the spindle with a headpiece so that this headpiece can engage the yarn at the lower end of the zone in which the twisting predominantly occurs.
The spindle headpiece, in the sense of the invention, can be a so-called spinning crown as has been described for example in French patent FR 1 002 510 or a so-called spinning finger as described in German patent DE 21 12 035 A1. The invention can be practiced with either of these types of head-pieces.
The purpose of the headpiece on the spindle, which can be the first part of the spindle engaging the yarn or thread, s to confine the yarn balloon during the spinning since the yarn, is wound around or engaged with the headpiece at one end and is paid onto the bobbin at some distance from this end so that significant spreading of the balloon is not possible. The ballooning outwardly is thereby greatly suppressed or reduced.
This reduction in ballooning is, therefore, in part a consequence of the looping of the yarn on the headpiece.
As a result of this balloon suppression effect, the yarn tension in the so-called spinning triangle at the output side of the output pair of rollers of the drafting frame does not depend exclusively on the twist and can contribute to a tendency toward thread breakage. In fact, as a practical matter it is noted that the thread breakage rate tends to increase with the spindle speed and to reduce at the lower spindle speeds.
Because of the looping of the yarn on the spindle headpiece and the looping of the yarn about the traveler on the ring, the yarn path can be treated as being subdivided into three zones each of which operates at a greater yarn tension than the preceding zone.
The first zone can be considered the so-called spinning zone between the output roller pair of the drafting frame and the spindle headpiece.
The second zone can be a so-called "balloon zone," between the spindle headpiece and the traveler.
The third zone can be considered a winding zone between the traveler and the bobbin which is formed on the core sleeve.
Since the yarn tension in the balloon zone is greater than that in the spinning zone and the yarn tension in the winding zone is greater than that in the balloon zone, but the invention concerns itself only with the development of the tension in the spinning zone, the balloon zone and the winding zone can be treated together as a single balloon/winding zone.
From French patent document FR 1,002,510, it is known to vary the distance between the thread guide and the spindle headpiece. It is there described that the position of the thread guide automatically can vary depending upon the build up of the bobbin on the spindle. A control of the position of the thread guide has not been described in any detail, nor is it apparent what effect the displacement of the thread guide can have.
In another system, the adjustment of the distance between the thread guide and the spindle headpiece (see Italian patent document IT 1 213 035) is effected to maintain the thread tension constant.
German patent document DE 25 43 581 A1, page 6, paragraph 2, teaches that varying the distance between the thread guide and the spindle headpiece can vary the number of turns with which the yarn is looped on the spindle headpiece.